The nanoparticles are structures with a size ranging from 1 to 100 nanometers and are especially attractive due to its optical, chemical, photoelectrochemical and electrical properties (Wilson M., Kannangara K., Smith G, Simmons M., Raguse B. Nanotechnology: Basic Science and Emerging Technologies. Chapman and Hall/CRC 2002; Jain, P. K., Huang, X., El-Sayed, I. H. El-Sayed, M. A. 2008. Noble metals on the nanoscale: optical and photothermal properties and some applications in imaging, sensing, biology and medicine. A of Chem Res. 41:1578-1586).
The synthesis of nanoparticles of different compositions and sizes is a field of investigation of great interest in the last years. Currently, the large scale production of AuNPs is carried out by chemical processes, which require the use of reducing agents to generate the particles from soluble gold salts. There are also physical processes, which require operating at reduced pressures and high temperatures. In both cases associated with AuNPs production, are produced chemical toxic compounds, due to the reactive agents and the operating conditions of the signaled systems; which present problems related to stability, aggregation and control of the desired size of the generated nanoparticles (Sau T. K., Murphy C. J. 2004. Room temperature, high-yield synthesis of multiple shapes of gold nanoparticles in aqueous solution. J Am Chem Soc 126:8648-8649).
Given the relevance of this topic worldwide, indispensable is the need to implement alternative and efficient processes for obtaining metallic nanoparticles that are “environmentally friendly” without requiring high quantities of energy. In this regard, biological systems are good candidates to do this. Currently, there are various publications on this topic, specifically related to the capacity of some organisms to generate these structures including bacteria and fungi (Brown S, Sarikaya M, Johnson E A. 2000. Genetic analysis of crystal growth. J Mol Biol 299: 725-735; Nair B, Pradeep T. 2002. Coalescence of nanoclusters and formation of submicron crystallites assisted by Lactobacillus strains. Cryst Growth Des 2: 293-298; Husseiny M I, Abd El-Aziz M, Badr Y, Mahmoud M A. 2007. Biosynthesis of gold nanoparticles using Pseudomonas aeruginosa. Spectrochimica Acta Part A 67: 1003-1006; Narayanan K B, Sakthivel N. 2010. Biological synthesis of metal nanoparticles by microbes. Adv Colloid Interface Sci 156: 1-13; Thirumurugan G, Veni V S, Ramachandran S, Rao J V, Dhanaraju M D. 2011. Superior wound healing effect of topically delivered silver nanoparticle formulation using eco-friendly potato plant pathogenic fungus: synthesis and characterization. J Biomed Nanotechnol. 7: 659-66; Mourato A, Gadanho M, Lino A R, Tenreiro R. 2011. Biosynthesis of crystalline silver and gold nanoparticles by extremophilic yeasts. Bioinorg Chem Appl. 2011: 546074; Balagurunathan R, Radhakrishnan M, Rajendran R B, Velmurugan D. 2011. Biosynthesis of gold nanoparticles by actinomycete Streptomyces viridogens strain HM10. Indian J Biochem Biophys 48: 331-335; Tikariha, S.; Singh, S.; Banerjee, S.; Vidyarthi, A. S. 2012. Biosynthesis of gold nanoparticles, scope and application: A review. IJPSR 3: 1603-1615).
The probable mechanisms by which peptides, bacteria, fungi, and plants catalyze the extracellular synthesis of metal nanoparticles have been recently revised (Durán N, Marcato P D, Durán M, Yadav A, Gade A, Rai M. 2011. Mechanistic aspects in the biogenic synthesis of extracellular metal nanoparticles by peptides, bacteria, fungi, and plants. Appl Microbiol Biotechnol 90: 1609-1624).
B. cinerea is a phytopathogenic fungus which infects a large number of vegetal species of great economic importance including fruit trees, ornamental plants and vegetables. This fungus produces a disease known as grey mold generating a serious problem on pre and postharvest in strawberries, raspberries, apples, pears, chestnuts, kiwi and grapes among others. In the grapevine, this fungus produces the bunch rot, (van Kan J. A. 2006. Licensed to kill: the lifestyle of a necrotrophic plant pathogen. Trends Plant Sci. 11, 247-253; Elad, Y., Williamson, B., Tudzynski, P. and Delen, N. eds. 2007. Botrytis: Biology, Pathology and Control. The Netherlands: Kluwer Academic Publishers).
Traditionally, B. cinerea has been studied with the objective of generating strategies to allow its control, and thus, to reduce the economic loss associated with the infections generated by the fungus. Up to today, there are no studies in nanotechnology field where cultures, propagules or molecules of B. cinerea are used in the process of synthesis of metallic nanoparticles. Our results show that B. cinerea in liquid medium is able to catalyze the synthesis of gold nanoparticles at room temperature from a solution of HAuCl4. The formation of nanoparticles is verified by the change of color of the reaction solution from pale yellow to reddish o purple. Moreover, the solutions containing the nanoparticles present a maximum of absortion at 540 nm, characteristic of the presence of this type of structures (Castro M E, Bravo M, Castillo A. 2012. Biosíntesis de nanopartículas de plata y oro por el hongo fitopatógeno Botrytis cinerea. XXI Congreso Latinoamericano de Microbiologia. Santos, Brasil. 28 de Octubre-1 de Noviembre).
Respect to the intellectual property, the patents related to synthesis of metallic nanoparticles mostly consist of the use of chemical processes for the synthesis of these structures, some of them allow the production of particles of a certain size and morphology. This is the case of the U.S. Pat. No. 6,929,675 in which is described a chemical system for the generation of copper, silver and gold nanoparticles. In specific relation with the AuNps, it is also possible to find some publications, like the patent US 20070125196, in which is disclosed the synthesis of AuNPs in a size ranging from 30 to 90 nm using a aqueous medium containing sodium acrylate and also the publication US 20060021468 in which is described a chemical process to control the uniformity of the generated particles.
Finally, it should be noted that although there are patents related to the use of biological systems for the synthesis of AuNps, there are currently no patents describing the use of B. cinerea or the molecules produced by said fungus for such purposes. In this context, the patent of greatest similarity is the patent published by a researcher of University of Illinois in the year 2010 (Publication US No. 20100055199), in which is described the use of the fungus Trichoderma reesei for the synthesis of AuNps.